THE ordinary farm crops on which the supply of food-stuffs depends seem to be produced best in regions where the rainfall varies between 20 and 35 inches per annum. Where the upper limit is exceeded in the British Islands, a good deal of pasture is found; on the other hand it is notable that the great wheat-producing districts, the eastern counties, are regions where the rainfall comes nearer to the lower limit. Special agricultural methods become necessary where there is less than 20 inches of rain, as is the case over large areas in Canada, Australia, India and South Africa. These methods fall into two groups:. irrigation is required if there is less than 10 inches of rain, while special cultural operations, collectively known as “dry farming,” are used when there is. as much as 15 or more inches. Between 10 to 15 inches, sometimes the one and sometimes the other method proves the more economical.